Virtual Storage Mirroring via Segment Segmentation and Mediator Control
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Solution Overview
Problem
In active/active virtual storage systems, data mismatching occurs due to simultaneous writing control by multiple controllers on different nodes, leading to inconsistencies in mirroring operations.
Innovation Solution
Implementing a controller that identifies and manages the writing and mirroring of data within specific segments, ensuring that each segment is controlled by a single node, thereby maintaining the order of write access and preventing data mismatching, and using a mirror control LUN to consolidate segments for efficient iSCSI session management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple controllers in an active/active system perform simultaneous writing control on the same virtual volume, then load distribution and quick recovery are improved, but data mismatching occurs in mirroring operations
Solution Approach 1:
The virtual volume is divided into multiple segments, and each segment is assigned to a specific controller for exclusive control. This segmentation prevents multiple controllers from simultaneously writing to the same segment, thereby avoiding data mismatching while still allowing load distribution across different controllers for different segments.
Solution Approach 2:
A segment assignment table acts as an intermediary data structure that records which controller is responsible for which segment. Before performing mirroring operations, controllers reference this table to determine the correct mirror destination controller, ensuring data consistency is maintained even in an active/active configuration.
2Reliability
If multiple controllers perform simultaneous mirroring operations on the same virtual volume, then availability is improved, but the complexity of controlling write order increases
Solution Approach 1:
By dividing the virtual volume into segments and assigning each segment to a specific controller, the system eliminates the need for complex global write ordering protocols. Each controller independently manages its assigned segments, significantly reducing control complexity while maintaining high availability through the active/active architecture.
Solution Approach 2:
Controllers autonomously determine their responsibilities by referencing the segment assignment table without requiring complex coordination with other controllers. This self-service approach simplifies the control mechanism while maintaining system availability, as each controller can independently perform mirroring operations for its assigned segments.
Data Source
AI summary
A virtualization controller identifies a node that manages a segment to be accessed, and instructs the node to access the segment. A mirror controller of the node instructed to access the segment writes data in the segment managed by the node and in a segment having a mirror relation with the segment managed by the node.